The present invention relates to a catheter for disposition within the urinary tract of a patient. More particularly, the invention concerns an indwelling drainage catheter.
The urinary tract of a patient includes the kidneys, ureters, bladder, urethra and, in men, the prostate which encircles the urethra adjacent the bladder. The bladder consists of the body, the trigone and the bladder neck. In the male, the urethra is typically divided into three sections—the prostatic, extending along about the upper 4 cm of the urethra; the membranous section, which narrows from the prostatic for about 1 cm; and the cavernous which continues to the glans for about 15 cm. The lumen of the urethra has a number of deep, irregular outpocketings, a multitude of glands, and a rich network of capillaries.
Problems in the urinary tract can have serious consequences, particularly when the problem is one of retention or incomplete emptying. Retention problems can result from any of a number of causes, including without limitation, spinal cord injury, typhoid, peritonitis, prostatic enlargement, urethral stricture, urethritis, cystitis, bladder tumors, or urethral calculus. Patients suffering from these and other conditions often require some interventional means to periodically drain or augment drainage of the bladder. Further, the clinician often requires indwelling urinary drainage to monitor urine production more closely, especially post-operatively. Failure to do so can result in damage of the epithelium and detrusor muscles associated with the bladder, and an increased potential for bacterial invasion which is commonly thought to contribute to urinary tract infection potentially leading to life-threatening urosepsis or kidney failure.
These urinary tract problems may manifest themselves with a variety of symptoms, such as: (i) incomplete emptying, (i.e., the patient is only able to urinate small volumes, e.g. <100 milliliters (ml), or has an elevated volume of urine left in the bladder following urination, e.g. >100 ml per attempt); (ii) experiencing frequent urges to urinate; (iii) intermittency (e.g. a patient's flow stops and starts often during urination); (iv) having a very weak and inconsistent urine flow stream; and (v) stress incontinence (e.g. leaking during lifting or straining as a result of excessive urine in the bladder or weakened sphincters).
Up to two million office visits annually in the United States are attributed to patients being bothered by some form of lower urinary tract symptoms (LUTS). For men, the symptoms are typically suspected to be caused by the intrusion of an enlarged prostate gland upon the urethra. Bladder outlet obstructions (BOO) are a major subgroup of LUTS. It is estimated that nearly 75% of men between the ages of 55 and 75 years have some degree of bladder outlet obstruction. Bladder outlet obstructions are primarily caused by the enlargement of the prostate gland (e.g., benign prostate hyperplasia (BHP)) which results in radial compression of the urethra surrounded thereby (i.e., the prostatic urethra), thus obstructing (i.e., constricting) urine flow, resulting in incomplete emptying of the bladder (i.e., there being what is clinically referred to as a “post void residual” (PVR) remaining in the bladder).
Devices have been developed to be positioned in the urethra and/or bladder to correct the problems of obstruction and incontinence of urine flow. Heretofore known problems associated with endourethral devices, more particularly critical device components such as stents, valve actuators, flow conduits, etc., generally relate to the physiology of the lower urinary tract (e.g., ingrowth, instability, pitting, depositions, etc.). Problems of device leakage or less than complete emptying of the bladder are widely encountered. Furthermore, issues surrounding device deployment and fit, positioning, repositioning, and retention (i.e., sufficient anchoring) have been well documented. Catheter associated urinary tract infections (CAUTI's) are frequently the result of legacy indwelling drainage devices and it is thought that up to 100,000 deaths/year can be attributed these devices.
It is especially critical that the endourethral device be stable with respect to position (i.e., deployed in a physiologically properly and stable position), and comfortable to wear, as the urinary tract is sensitive to contact and friction. Inter-urethral stents have been utilized within the prostatic region, although many users foregoing such devices for alternate therapies due to feelings of discomfort and/or pain. Many endourethral devices have similarly been evaluated for urinary incontinence for females. Based upon clinical findings, many have been shown to be uncomfortable, thus severely retarding their utility as a therapy. Other devices have migrated into the bladder, or have been expelled under straining conditions.
One common drainage catheter is the Foley catheter and variations thereof. The traditional Foley catheter includes an inflatable balloon at the distal end of a catheter tube, as depicted in FIG. 1. The balloon is deflated as the tube is advanced up the urethra toward the bladder. Once the balloon traverses the bladder sphincter, the balloon is inflated to prevent only anterograde movement of the catheter within the urethra. The proximal end incorporates a drainage inlet port in communication with the catheter lumen for draining urine from the bladder. The distal end also includes an inflation lumen that is adapted to engage a source of saline for inflating the balloon in situ. The distal end protrudes beyond the urethral orifice and can be attached to a receptacle for collection of the nearly constantly dripping urine. Optionally, a plug or valve may be incorporated at the distal end to stop the flow of urine. While the traditional Foley catheter uses a balloon for retention, variations have incorporated alternative elements that are expandable and contractible within the bladder. These variations all require an additional lumen for passage of a control component for controlling the expansion or contraction of the alternative element within the bladder.
One problem associated with the Foley-type catheter is that the retention balloon or element rests against the dome of the bladder an area thought to be only three cells thick. Placement of a retention device in this region often leads to pooling of urine, or dead space, and may be partially responsible for the multitude of infections caused by this device. This aspect can also cause tissue compression and irritation of the sensitive tissue lining the bladder, sometimes leading to erosion of the tissue. The pressure of the retention element may also aggravate the micturition reflex, or the electrical signal to urinate. The bladder contracts in response to this signal, which leads to further pressure and irritation at the area of contact between the bladder and the retention element. These bladder contractions can further result in oscillation of the catheter proximally and distally since there is no anchoring the catheter to prevent movement in the proximal direction. In some cases, inadequate deflation or retraction of the retention element can occur, leading to extreme discomfort and even damage to the urethra upon withdrawal. The presence of the additional lumen for introduction of inflation fluid or other actuation feature for the catheter dramatically reduces the flow area of the drainage lumen.
Another problem associated with the Foley-type drainage catheter is that the balloon or other retention element only prevents retrograde movement, or movement distally toward the urethral orifice. The retention element does not prevent movement of the retention element and catheter deeper into the bladder. Obviously, excessive distal movement of the catheter may cause physical damage to the bladder. Irritation or abrading of the mucosa within the urethra may also result by the continuous sliding back and forth of the catheter within the urethra.
However, a more insidious result of this distal movement is the increased instance of urinary tract infections. It has been suggested that the increase in infection rate for long indwelling catheter patients is due to migration of bacteria up the urethra, coined “biofilm creep.” In particular, it is believed that bacteria infecting the distal end of the drainage catheter can be carried into the urethra by each proximal movement of the catheter. As the bacteria are advanced upward by this proximal movement, they adhere to the tissue of the urethra. Some of the bacteria hold their position as the catheter resets distally, only to hitch a ride again when the catheter again moves proximally toward the bladder. It has been suggested that this biofilm creep mechanism allows bacteria to travel from the urethral orifice to the bladder in a matter of minutes. Urine that would otherwise help “flush” the urethra is isolated from the urethra as it passes through the drainage lumen of the Foley catheter.
It is expected that an increasing number of long-term drainage catheterizations will occur, especially as patients live longer. Conventional drainage catheters are not designed for prevent expensive and life threatening infections. There is a significant need for a urinary drainage catheter that avoids these problems associated with the Foley-type catheter.